The present invention relates to a process for working up municipal plastic waste materials by gasification.
About 3.5 million tons of plastic are produced in Germany, of which a predominant portion is used for packaging and, after use, is disposed in garbage. Prior to the introduction of the so-called dual system it was common that this plastic waste together with the standard municipal garbage was either deposited in a dump or was burned in a garbage incineration plant. With the introduction of the dual system efforts are made to collect the plastic waste separately from the common components of the garbage and to recycle them and/or reutilize them. Thus plastic waste substantially contains carbon and hydrogen and has the same heat content as a heavy heating oil. A maximum of 2.5 million tons of plastic waste can be collected per year in Germany.
Narrow limits are however placed on the direct reutilization of these plastic waste materials, since the collected plastic waste materials include a mixture of different compounds, which cannot be separated sufficiently into their individual polymer components. Plastic materials used in individual applications, such as e.g. in the packaging industry, the automobile industry or the construction industry, must have exact and definite properties, which only can be achieved with pure plastics. Furthermore reutilized plastic material cannot therefor fulfill these qualitative requirements, because a qualitative reduction in the properties always accompanies the repetition of an already once completed process step.
It is thus obvious to use the energy content of the plastic waste by combustion to produce heat, as is done in the garbage incineration plant. Opposing this however is the fact that plastic waste material always contains halogen-containing substances, e.g. PVC, which leads to formation of hydrochloric acid and more or less amounts of polycyclic halogen-containing compounds (dioxins and/or furans), which are released to the atmosphere in the exhaust gases. The removal of these harmful substances from the exhaust gases is however only possible with comparatively great expense. The danger exists that if the exhaust gas wash process is interrupted in operation, these harmful substances can be released at least for a limited time to the atmosphere.